New --plugins-dir=plugins/ option (#212)

* New --plugins-dir=plugins/ option

New option causing Datasette to load and evaluate all of the Python files in
the specified directory and register any plugins that are defined in those
files.

This new option is available for the following commands:

    datasette serve mydb.db --plugins-dir=plugins/
    datasette publish now/heroku mydb.db --plugins-dir=plugins/
    datasette package mydb.db --plugins-dir=plugins/

* Unit tests for --plugins-dir=plugins/

Closes #211

datasette/app.py

@@ -31,6 +31,7 @@
     get_all_foreign_keys,
     is_url,
     InvalidSql,
+    module_from_path,
     path_from_row_pks,
     path_with_added_args,
     path_with_ext,
@@ -1032,7 +1033,7 @@ def __init__(
             self, files, num_threads=3, cache_headers=True, page_size=100,
             max_returned_rows=1000, sql_time_limit_ms=1000, cors=False,
             inspect_data=None, metadata=None, sqlite_extensions=None,
-            template_dir=None, static_mounts=None):
+            template_dir=None, plugins_dir=None, static_mounts=None):
         self.files = files
         self.num_threads = num_threads
         self.executor = futures.ThreadPoolExecutor(
@@ -1048,7 +1049,20 @@ def __init__(
         self.sqlite_functions = []
         self.sqlite_extensions = sqlite_extensions or []
         self.template_dir = template_dir
+        self.plugins_dir = plugins_dir
         self.static_mounts = static_mounts or []
+        # Execute plugins in constructor, to ensure they are available
+        # when the rest of `datasette inspect` executes
+        if self.plugins_dir:
+            for filename in os.listdir(self.plugins_dir):
+                filepath = os.path.join(self.plugins_dir, filename)
+                with open(filepath) as f:
+                    mod = module_from_path(filepath, name=filename)
+                    try:
+                        pm.register(mod)
+                    except ValueError:
+                        # Plugin already registered
+                        pass
 
     def app_css_hash(self):
         if not hasattr(self, '_app_css_hash'):

datasette/cli.py

@@ -58,13 +58,14 @@ def inspect(files, inspect_file, sqlite_extensions):
 @click.option('--force', is_flag=True, help='Pass --force option to now')
 @click.option('--branch', help='Install datasette from a GitHub branch e.g. master')
 @click.option('--template-dir', type=click.Path(exists=True, file_okay=False, dir_okay=True), help='Path to directory containing custom templates')
+@click.option('--plugins-dir', type=click.Path(exists=True, file_okay=False, dir_okay=True), help='Path to directory containing custom plugins')
 @click.option('--static', type=StaticMount(), help='mountpoint:path-to-directory for serving static files', multiple=True)
 @click.option('--title', help='Title for metadata')
 @click.option('--license', help='License label for metadata')
 @click.option('--license_url', help='License URL for metadata')
 @click.option('--source', help='Source label for metadata')
 @click.option('--source_url', help='Source URL for metadata')
-def publish(publisher, files, name, metadata, extra_options, force, branch, template_dir, static, **extra_metadata):
+def publish(publisher, files, name, metadata, extra_options, force, branch, template_dir, plugins_dir, static, **extra_metadata):
     """
     Publish specified SQLite database files to the internet along with a datasette API.
 
@@ -94,7 +95,7 @@ def _fail_if_publish_binary_not_installed(binary, publish_target, install_link):
 
     if publisher == 'now':
         _fail_if_publish_binary_not_installed('now', 'Zeit Now', 'https://zeit.co/now')
-        with temporary_docker_directory(files, name, metadata, extra_options, branch, template_dir, static, extra_metadata):
+        with temporary_docker_directory(files, name, metadata, extra_options, branch, template_dir, plugins_dir, static, extra_metadata):
             if force:
                 call(['now', '--force'])
             else:
@@ -110,7 +111,7 @@ def _fail_if_publish_binary_not_installed(binary, publish_target, install_link):
             click.confirm('Install it? (this will run `heroku plugins:install heroku-builds`)', abort=True)
             call(["heroku", "plugins:install", "heroku-builds"])
 
-        with temporary_heroku_directory(files, name, metadata, extra_options, branch, template_dir, static, extra_metadata):
+        with temporary_heroku_directory(files, name, metadata, extra_options, branch, template_dir, plugins_dir, static, extra_metadata):
             create_output = check_output(
                 ['heroku', 'apps:create', '--json']
             ).decode('utf8')
@@ -190,13 +191,14 @@ def skeleton(files, metadata, sqlite_extensions):
 @click.option('--extra-options', help='Extra options to pass to datasette serve')
 @click.option('--branch', help='Install datasette from a GitHub branch e.g. master')
 @click.option('--template-dir', type=click.Path(exists=True, file_okay=False, dir_okay=True), help='Path to directory containing custom templates')
+@click.option('--plugins-dir', type=click.Path(exists=True, file_okay=False, dir_okay=True), help='Path to directory containing custom plugins')
 @click.option('--static', type=StaticMount(), help='mountpoint:path-to-directory for serving static files', multiple=True)
 @click.option('--title', help='Title for metadata')
 @click.option('--license', help='License label for metadata')
 @click.option('--license_url', help='License URL for metadata')
 @click.option('--source', help='Source label for metadata')
 @click.option('--source_url', help='Source URL for metadata')
-def package(files, tag, metadata, extra_options, branch, template_dir, static, **extra_metadata):
+def package(files, tag, metadata, extra_options, branch, template_dir, plugins_dir, static, **extra_metadata):
     "Package specified SQLite files into a new datasette Docker container"
     if not shutil.which('docker'):
         click.secho(
@@ -207,7 +209,7 @@ def package(files, tag, metadata, extra_options, branch, template_dir, static, *
             err=True,
         )
         sys.exit(1)
-    with temporary_docker_directory(files, 'datasette', metadata, extra_options, branch, template_dir, static, extra_metadata):
+    with temporary_docker_directory(files, 'datasette', metadata, extra_options, branch, template_dir, plugins_dir, static, extra_metadata):
         args = ['docker', 'build']
         if tag:
             args.append('-t')
@@ -233,8 +235,9 @@ def package(files, tag, metadata, extra_options, branch, template_dir, static, *
 @click.option('--inspect-file', help='Path to JSON file created using "datasette inspect"')
 @click.option('-m', '--metadata', type=click.File(mode='r'), help='Path to JSON file containing license/source metadata')
 @click.option('--template-dir', type=click.Path(exists=True, file_okay=False, dir_okay=True), help='Path to directory containing custom templates')
+@click.option('--plugins-dir', type=click.Path(exists=True, file_okay=False, dir_okay=True), help='Path to directory containing custom plugins')
 @click.option('--static', type=StaticMount(), help='mountpoint:path-to-directory for serving static files', multiple=True)
-def serve(files, host, port, debug, reload, cors, page_size, max_returned_rows, sql_time_limit_ms, sqlite_extensions, inspect_file, metadata, template_dir, static):
+def serve(files, host, port, debug, reload, cors, page_size, max_returned_rows, sql_time_limit_ms, sqlite_extensions, inspect_file, metadata, template_dir, plugins_dir, static):
     """Serve up specified SQLite database files with a web UI"""
     if reload:
         import hupper
@@ -262,6 +265,7 @@ def serve(files, host, port, debug, reload, cors, page_size, max_returned_rows,
         metadata=metadata_data,
         sqlite_extensions=sqlite_extensions,
         template_dir=template_dir,
+        plugins_dir=plugins_dir,
         static_mounts=static,
     )
     # Force initial hashing/table counting

datasette/utils.py

@@ -1,6 +1,7 @@
 from contextlib import contextmanager
 import base64
 import hashlib
+import imp
 import json
 import os
 import re
@@ -182,14 +183,16 @@ def escape_sqlite(s):
         return '[{}]'.format(s)
 
 
-def make_dockerfile(files, metadata_file, extra_options, branch, template_dir, static):
+def make_dockerfile(files, metadata_file, extra_options, branch, template_dir, plugins_dir, static):
     cmd = ['"datasette"', '"serve"', '"--host"', '"0.0.0.0"']
     cmd.append('"' + '", "'.join(files) + '"')
     cmd.extend(['"--cors"', '"--port"', '"8001"', '"--inspect-file"', '"inspect-data.json"'])
     if metadata_file:
         cmd.extend(['"--metadata"', '"{}"'.format(metadata_file)])
     if template_dir:
         cmd.extend(['"--template-dir"', '"templates/"'])
+    if plugins_dir:
+        cmd.extend(['"--plugins-dir"', '"plugins/"'])
     if static:
         for mount_point, _ in static:
             cmd.extend(['"--static"', '"{}:{}"'.format(mount_point, mount_point)])
@@ -216,7 +219,7 @@ def make_dockerfile(files, metadata_file, extra_options, branch, template_dir, s
 
 
 @contextmanager
-def temporary_docker_directory(files, name, metadata, extra_options, branch, template_dir, static, extra_metadata=None):
+def temporary_docker_directory(files, name, metadata, extra_options, branch, template_dir, plugins_dir, static, extra_metadata=None):
     extra_metadata = extra_metadata or {}
     tmp = tempfile.TemporaryDirectory()
     # We create a datasette folder in there to get a nicer now deploy name
@@ -242,6 +245,7 @@ def temporary_docker_directory(files, name, metadata, extra_options, branch, tem
             extra_options,
             branch,
             template_dir,
+            plugins_dir,
             static,
         )
         os.chdir(datasette_dir)
@@ -255,6 +259,11 @@ def temporary_docker_directory(files, name, metadata, extra_options, branch, tem
                 os.path.join(saved_cwd, template_dir),
                 os.path.join(datasette_dir, 'templates')
             )
+        if plugins_dir:
+            link_or_copy_directory(
+                os.path.join(saved_cwd, plugins_dir),
+                os.path.join(datasette_dir, 'plugins')
+            )
         for mount_point, path in static:
             link_or_copy_directory(
                 os.path.join(saved_cwd, path),
@@ -267,7 +276,7 @@ def temporary_docker_directory(files, name, metadata, extra_options, branch, tem
 
 
 @contextmanager
-def temporary_heroku_directory(files, name, metadata, extra_options, branch, template_dir, static, extra_metadata=None):
+def temporary_heroku_directory(files, name, metadata, extra_options, branch, template_dir, plugins_dir, static, extra_metadata=None):
     # FIXME: lots of duplicated code from above
 
     extra_metadata = extra_metadata or {}
@@ -314,6 +323,13 @@ def temporary_heroku_directory(files, name, metadata, extra_options, branch, tem
                 os.path.join(tmp.name, 'templates')
             )
             extras.extend(['--template-dir', 'templates/'])
+        if plugins_dir:
+            link_or_copy_directory(
+                os.path.join(saved_cwd, plugins_dir),
+                os.path.join(tmp.name, 'plugins')
+            )
+            extras.extend(['--plugins-dir', 'plugins/'])
+
         if metadata:
             extras.extend(['--metadata', 'metadata.json'])
         for mount_point, path in static:
@@ -625,3 +641,13 @@ def link_or_copy_directory(src, dst):
         shutil.copytree(src, dst, copy_function=os.link)
     except OSError:
         shutil.copytree(src, dst)
+
+
+def module_from_path(path, name):
+    # Adapted from http://sayspy.blogspot.com/2011/07/how-to-import-module-from-just-file.html
+    mod = imp.new_module(name)
+    mod.__file__ = path
+    with open(path, 'r') as file:
+        code = compile(file.read(), path, 'exec', dont_inherit=True)
+    exec(code, mod.__dict__)
+    return mod

tests/fixtures.py

@@ -15,12 +15,16 @@ def app_client():
         conn = sqlite3.connect(filepath)
         conn.executescript(TABLES)
         os.chdir(os.path.dirname(filepath))
+        plugins_dir = os.path.join(tmpdir, 'plugins')
+        os.mkdir(plugins_dir)
+        open(os.path.join(plugins_dir, 'my_plugin.py'), 'w').write(PLUGIN)
         ds = Datasette(
             [filepath],
             page_size=50,
             max_returned_rows=100,
             sql_time_limit_ms=20,
             metadata=METADATA,
+            plugins_dir=plugins_dir,
         )
         ds.sqlite_functions.append(
             ('sleep', 1, lambda n: time.sleep(float(n))),
@@ -90,6 +94,20 @@ def generate_sortable_rows(num):
     }
 }
 
+PLUGIN = '''
+from datasette import hookimpl
+import pint
+
+ureg = pint.UnitRegistry()
+
+
+@hookimpl
+def prepare_connection(conn):
+    def convert_units(amount, from_, to_):
+        "select convert_units(100, 'm', 'ft');"
+        return (amount * ureg(from_)).to(to_).to_tuple()[0]
+    conn.create_function('convert_units', 3, convert_units)
+'''
 
 TABLES = '''
 CREATE TABLE simple_primary_key (

tests/test_api.py

@@ -588,8 +588,10 @@ def test_row_foreign_key_tables(app_client):
 
 
 def test_unit_filters(app_client):
-    response = app_client.get('/test_tables/units.json?distance__lt=75km&frequency__gt=1kHz',
-                              gather_request=False)
+    response = app_client.get(
+        '/test_tables/units.json?distance__lt=75km&frequency__gt=1kHz',
+        gather_request=False
+    )
     assert response.status == 200
     data = response.json
 
@@ -598,3 +600,11 @@ def test_unit_filters(app_client):
 
     assert len(data['rows']) == 1
     assert data['rows'][0][0] == 2
+
+
+def test_plugins_dir_plugin(app_client):
+    response = app_client.get(
+        "/test_tables.json?sql=select+convert_units(100%2C+'m'%2C+'ft')",
+        gather_request=False
+    )
+    assert pytest.approx(328.0839) == response.json['rows'][0][0]

tests/test_utils.py

@@ -195,6 +195,7 @@ def test_temporary_docker_directory_uses_hard_link():
             extra_options=None,
             branch=None,
             template_dir=None,
+            plugins_dir=None,
             static=[],
         ) as temp_docker:
             hello = os.path.join(temp_docker, 'hello')
@@ -218,6 +219,7 @@ def test_temporary_docker_directory_uses_copy_if_hard_link_fails(mock_link):
             extra_options=None,
             branch=None,
             template_dir=None,
+            plugins_dir=None,
             static=[],
         ) as temp_docker:
             hello = os.path.join(temp_docker, 'hello')